1. Field of the Invention
The present invention relates to a contact force sensor package for detecting the sphygmus wave of a human body to measure blood pressure, blood pressure meter with the contact force sensor package, and a method for fabricating the contact force sensor package.
2. Description of the Related Art
A blood pressure meter is a device to measure blood pressure using the relationship between the blood pressure and a sphygmus wave according to the repeated contraction of a heart. The blood pressure meter includes a contact force sensor package.
FIG. 1 is a cross-sectional view of an example of a typical contact force sensor package 50. Referring to FIG. 1, the contact force sensor package 50 contacts a wrist 1 where a radial artery 5 passes to detect a sphygmus wave. In the contact force sensor package 50, a substrate layer 54 having a thin film 55 is mounted on a circuit substrate layer 51 and the substrate layer 54 having the thin film 55 and the circuit substrate layer 51 are electrically connected via a bonding wire 60. To protect the bonding wire 60, the substrate layer 54 is sealed with an elastic material such as a silicon gel 65.
A vibration, that is, a sphygmus wave, generated from the radial artery 5 is transferred to the thin film 55 via the silicon gel 65. Accordingly, blood pressure is measured through a change of the thin film 55. However, since the bonding wire 60 that is tens of nanometers thick is weak to an impact, to prevent disconnection of the bonding wire 60 due to the vibration transferred to the silicon gel 65, the silicon gel 65 on the thin film 55 is formed to have a thickness M that is relatively thick.
For this reason, it is difficult to reduce the size of the contact force sensor package. Also, as the distance between the radial artery and the thin film increases, the sensitivity of detection of the sphygmus wave is deteriorated.